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June 5, 1997 <br /> Vapor Extraction Evaluation confirmation sample borings Vapor extraction is continuing <br /> July 31, 1997 <br /> Continue using Carbon Adsorption for vapor recovery off gas control Carbons system has <br /> removed an estimated 31 gallons of gasoline range hydrocarbons, Venting of MW$ (offsite well) <br /> has removed an additional 0 79 gallons of TPHg, for a total of 12096 5 gallons of TPHg removed <br /> from free product recovery and vapor extraction <br /> Effectiveness of Vapor Extraction System on Impacted Soils and Groundwater <br /> In a letter dated October 11, 1996, San Joaquin County Health requested a work plan to drill and <br /> sample soil borings to evaluate the effectiveness of the operating vapor extraction system Western <br /> Geo-Engineers submitted this work plan and approval of the work plan was addressed in the <br /> February 3, 1997 letter from San Joaquin County Health, see Appendix A <br /> Figure 4 is a revised Fence Diagram showing formation lithology with historic groundwater high and <br /> low Currently, monitor wells MW I, MW2, MW3 and MW10 are being used for vapor recovery. <br /> Newly installed well MW13 (SB7) will also be used for vapor recovery MW13 along with MW2 <br /> and MW10 will also be used for air sparging when groundwater is too high for proper vapor <br /> extraction <br /> Siting of sample horings <br /> Sample borings SB4, SBS, SB6 and SB7 were sited near historic high concentrations of soil and <br /> groundwater contamination (SBI, SB2, SB3, MW2, MW3 and MW10), and away from the wells <br /> that are currently being used for vapor extraction SB4 was sited approximately five feet west of <br /> SBI in a downgradient direction SB5 was placed between MW2 and MW3 and downgradient of <br /> MW1.0 SB6 was placed approximately five feet southeast of SB3 in the downgradient direction <br /> SB7 was placed north of SB5 approximately five feet and converted into a vapor extraction/sparging <br /> well, see Figure 3 <br /> Drilling Method/Well Construction <br /> Confirmation soil sample borings SB4, SB5, SB6 and SB6 were drilled on June 4 and 5, 1997. <br /> Western Geo-Engineers subcontracted Woodward Drilling (C57 — 710079) who used a truck <br /> 4 <br />